(1) Field of the Invention
This invention relates to a method for making artificial snow, and to a skiing slope using such snow.
(2) Description of the Prior Art
In certain ski resorts around the world, artificial skiing slopes are produced by a number of different techniques.
One method is to create artificial snow by using machines which spray atomised water and compressed air (or other gas) into a subzero atmosphere to create a blanket of snow. The adiabatic expansion of the air absorbs heat from the atomised water and the particles freeze to form snow flakes. The machines are expensive to install and operate, requiring large volumes of compressed air and are only capable of producing skiable snow when both the air and ground temperatures are below 0.degree. C. to prevent the snow from melting. In spite of the large capital and operating costs, such machines are currently in use as they can extend the skiing season by up to one month in certain resorts.
The basic method for producing snow using this type of technique was disclosed in U.S. Pat. No, 2,676,471 (Pierce). Improved methods and apparatus for this technique are disclosed in U.S. Pat. Nos. 3,716,190 (Lindlof); 3,010,660 (Barnett); 3,301,485 (Tropeano); 3,298,612 (Torrens); 3,761,020 (Tropeano et al); 3,774,843 (Rice); 3,774,842 (Howell); 3,945,567 (Rambach); 4,004,732 (Hanson); 4,083,492 (Dewey); 4,105,161 (Kircher et al); and 3,733,029 (Eustis et al) and Australian Patent Application Nos. 77956/75 (Burns) and 12534/83 (Albertson).
The atomised water particles can be fed into an airflow generated by a fan (e.g. as shown in U.S. Pat. Nos. 3,760,598 (Jakob et al) and 2,968,164 (Hanson) and the formation of the snow flakes or crystals can be accelerated by seeding with nucleating agents such as ice crystals (see U.S. Pat. No. 3,596,476 (Jakob et al) and bacteria (see U.S. Pat. No. 4,200,228 (Woerpel).
To prevent the artificial snow from melting, U.S. Pat. No. 3,893,507 (MacCracken et al) and Austrian Patent No. 363962 (Michaelis) disclose methods of freezing or cooling the ground using refrigeration systems of the type used for skating rinks and in mining. These methods do not overcome the problem of the snowflakes melting in the air and the constant refrigeration of the snow formed e.g. by the Pierce method, will eventually turn to a glaze of ice, unsuitable for skiing, as heat from the air above the snow is absorbed via the snow to the refrigeration.
In more temperate zones, artificial skiing slopes have been developed using mats, bristles or carpets of synthetic materials. Such slopes are sold under the Trade Marks "Dendex", "Delta", and "Dri-Sno" and form the subject of U.S. Pat. Nos. 3,400,643 (Holley) and 3,731,923 (Grieve) and Australian Patent Application No. 71499/74 (Snow Products Inc). These slopes require the use of special skis and poles and cannot truly recreate a snow-covered slope.